The invention relates to a novel wetting agent for use particularly but in a non-limiting manner, in the field of cosmetics, for its aptitude to wet pigments. This property is particularly sought after in compositions requiring a dispersion of pigments. This is the case in particular of solar products and make-up products. It is also useful in make-up cleansing products to promote the fixation and removal of the pigments present on the skin.
Numerous products are proposed for their aptitude to wet pigments. C12-C15 alkyl benzoate and isopropyl palmitate are known in particular. Also used for this function are certain triglycerides, such as castor oil and glycerol tricaprylocaprate.
Document EP-A-792 633 describes a powdery anhydrous composition comprising a binder or wetting agent. In practice, the binder is an ester, liquid at ambient temperature, comprising at least two hydrocarbon chains, each comprising at least ten carbon atoms. The ester in question does not have a hydroxyl group. A preferred agent is, for example, glycerol triisostearate.
All the wetting agents known to the Applicant, as previously listed, have a number of drawbacks. Firstly, the quantity of raw material required to wet a given pigment remains relatively high. It affects the formulation in terms of cost, composition and sensory properties. The high viscosity of certain raw materials, such as castor oil, at ambient temperature, or of the pigment dispersions obtained, make these products difficult to handle. Finally, the known wetting agents confer a sometimes greasy touch on the final composition into which they are introduced.
In other words, a need exists, particularly for the cosmetics market, for products having a wetting power that does not have the above drawbacks.
In the course of its researches, the Applicant found that mixtures of monoesters and diesters of butylene glycol, including for example butylene glycol cocoate, had a higher wetting power than that of the known agents.
Butylene glycol cocoate (BGC) is a known product, already used as a cosmetic ingredient in a composition, marketed by the Applicant under the trade name EMULFREE® CBG. More precisely, this composition corresponds to the combination of BGC with isostearyl alcohol and ethylcellulose. In practice, EMULFREE® CBG is used as a stabilizer of the oily phase in the oil-in-water emulsions. The role of the butylene glycol cocoate in this composition is confined to the solubilization of the gelling polymer, that is ethylcellulose. In other words and contrary to the invention, butylene glycol cocoate is not suitable for direct mixing with fillers but is necessarily used in combination with a fatty alcohol (isostearyl alcohol) in the presence of a polymer (ethylcellulose).
The mixture of the invention is clearly distinguished not only in terms of function, but also in terms of structure, from the butylene glycol esters described in document EP-A-860 164. In fact, the document describes the combination of a chemical UV filter with butylene glycol diesters only, with fatty acids containing 6 to 12 carbon atoms. Not only does the composition not contain monoesters, but furthermore, it is used as a chemical filter solubilizing agent and not as a wetting agent.
Document JP 57072907 describes a make-up cleansing product based either on monoesters or on diesters containing 17 to 36 carbon atoms. Here also, the mixture of monoesters and diesters is not also considered. Moreover, in the case of the diesters, they are diacid esters, that is, of an acid esterified by two alcohols and not a diol esterified by two acids, as is the case of the invention. As to the monoesters, they issue from a monoacid with a monoalcohol and not from a monoester of a diol.
Document EP-A-651 990 describes the use of esters in a make-up cleansing composition. According to this document, the esters used are also either monoalcohol esters, or diesters. In practice, they are obtained from an alcohol containing 1 to 17 carbon atoms and a fatty acid containing 3 to 18 carbon atoms. Moreover, they must have a free hydroxyl group.
Document EP-A-1 230 910 describes an oil-in-water emulsion containing pigments, whereof the oily phase only contains caprylocaprate diesters of butylene glycol.
In other words, nothing in the prior art known to the Applicant discloses the idea of using a mixture of monoesters and diesters of butylene glycol, as a wetting agent.